Racial differences in the burden of cardiovascular disease contribute significantly to health disparities observed in the United States. Timely access to emergency care is critical for diseases such as acute myocardial infarction (AMI) and congestive heart failure (CHF), yet access to emergency departments (EDs) varies substantially across communities. The deterioration of ED access, due to either ED closure or crowding (henceforth ED access block), is associated with increased mortality rates. It has been posited that ED closures may improve acute care by removing poor-performers in a competitive market such that there is a tradeoff between distance traveled and quality of care. The risk of this assumption however, is that if ED closures occur mainly in minority communities, there could be differential effects on minority communities. We seek to fill this gap in the literature. Our long-term goal is to identify system-level mechanisms in emergency care delivery that contribute to disparities across various segments of the population. Our objectives are (1) to identify whether ED access block is a possible contributor to the widening of process and health outcome disparities between black and white patients with CHF and AMI; and (2) whether improved access (as a result of ED openings) may reduce disparities. We will link Medicare claims, hospital surveys, location data, and daily ambulance diversion logs from 2001 to 2010 to address the following Specific Aims (sample size is ~6 million admissions): Aim 1: Determine whether ED access block disproportionately affects minority patients relative to others within a community and whether ED openings can reduce those disparities. We hypothesize that ED access block results in a higher percentage of black patients being admitted to facilities with lower level technology, receiving inferior treatment, and experiencing worse patient outcomes as compared to white patients. Aim 2: Determine whether ED access block disproportionately affects minority-serving hospitals and whether ED openings can reduce disparities. We hypothesize that minority-serving hospitals are disproportionately burdened with a higher patient load and experience deteriorating quality relative to other facilities with the same level of ED access block. Aim 3: Determine whether ED access block disproportionately affects minority-heavy communities and whether ED openings can reduce disparities. We hypothesize that minority-heavy communities experience reduced technology access and quality relative to others when exposed to ED access block. Achieving these aims will offer an unusually complete picture of the potential mechanisms through which disparities can occur at patient-, facility-, and community-levels. Such mechanisms will inform policy makers whether certain measures are needed to improve efficiency of care and minimize disparities. Our framework can be applied broadly to investigate other types of disparities where ED access is critical.